Automatic balancing device

ABSTRACT

An automatic balancing device for rotary units or systems. The automatic balancing device includes an annular housing, and an annular outer race track disposed in the annular housing. The outer race track is concentric with and attachable to the rotary system so as to rotate with the rotary system. A number of roller bodies are disposed in the annular housing and are freely movable along the race track for dynamic and/or static contact therewith during rotation of the rotary unit or system. The outer racetrack is provided in a separate ring of a large diameter having a torus-shaped groove forming the race track and having a curved concave profile facing the center of the separate ring.

DESCRIPTION OF THE RELATED ART

The present invention refers to an auto-balancing device for rotaryunits or systems, having an annular outer race track disposed in aclosed, substantially annular housing arranged substantially concentricwith and attached to the rotary unit or system, for rotating with therotary unit or system, and a number of rolling bodies disposed in thehousing and freely movable along the race track for dynamic and/orstatic contact therewith during rotation of the rotary system.

SUMMARY OF THE INVENTION

In different rotary units or systems, such as rotating washing machinedrums, bladed ceiling fans, vehicle wheels, etcetera, there occur largeunbalance forces, which should be eliminated as far as possible to givea reduced operation noise for the rotary system, a reduction ofvibrations, thereby also reducing the necessity of using otherstabilizing means, such as heavy machine beds, etcetera, and also toallow a high rotational speed, which at least for a washing machinedrum, is essential for obtaining a desired centrfugal force forexpelling water from the material washed in the machine, and forpreventing damages to the machine base and the shaft bearings whereinthe rotary system is supported. For this purpose it has earlier beenproposed auto-balancing devices having a ringformed, sealed andfluid-filled chamber and inserted therein a number of rolling bodies notfilling more than a portion of the said chamber and moving independentlyto different positions along the annular chamber to counter-actunbalance during rotation.

Thus U.S. Pat. No. 2,984,094 refers to a washing machine having a racetrack formed by a flat steel band applied elastically to the wall of thehousing. The large rolling elements used in this earlier known devicethus roll against a flat surface, whereby the rolling bodies have smallstability in the axial direction.

GB-A-832,048 proposes for a similar purpose using commercially availableanti-friction bearing parts as housing and race track for suchauto-balancing devices, but such solutions would be very expensive andheavy if used in large diameter applications.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide an auto-balancingdevice for rotary systems, by means of which the rolling bodies willhave a radially and axially exactly positioned race track, therebyreducing contact stresses, whereas the entire device is simple andtherefore highly flexible in design and provides an efficient and yetin-expensive solution. This has been obtained by a device having thefeatures described below.

BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter the invention will be further described with reference toembodiments shown in the accompanying drawings.

FIG. 1 shows schematically a washing machine drum, with bearings andauto-balancing devices according to the invention intimated one at eachgable wall of the drum.

FIG. 2 is a larger scale cross-sectional view through a portion of theauto-balancing device intimated in FIG. 1, taken along the line 2--2 ofFIG. 1.

FIG. 3 shows schematically a planar view of one embodiment of a racetrack ring forming part of the auto-balancing device according to theinvention,

FIG. 4 is a modified embodiment of an auto-balancing device according tothe invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows in a diagrammatic manner a rotary system, such as acylindrical washing machine drum 1, having concentric stub axles 2extending one form each gable wall of the drum 1 and being journalled ina housing (not shown) in rolling bearings 3. It is evident that such arotary system, will be subjected to large unbalance forces duringrotation as the washing goods seldom will be evenly distributedthroughout the drum, but will often gather at a small sector of thedrum, displaced and well spaced from the centre of the drum. Similarphenomena caused by manufacturing tolerances, by dirt and the like,applies also to other types of rotary systems, such as bladed ceilingfans, vehicle wheels and the like. For compensating and reducing theunbalance each gable region of the drum in the embodiment according toFIG. 1, therefore is provided with an autobalancing device 4 accordingto one embodiment of the present invention. Each one of theseautobalancing devices 4 is constituted by an annular housing 4apositioned concentric with the centre axis A of the washing machinedrum 1. The housing 4a of the autobalancing device in FIG. 1 isillustrated as having a quadrangular cross-section, but as shown lateron, this cross-section might be of other forms, e.g. circular, etcetera.

FIG. 2 illustrates a cross-section through a first embodiment of theautobalancing device 4 according to the invention.

In the embodiment shown in FIG. 2 the autobalancing device 4 has ahousing constituted by a first housing 4a half shaped as a substantiallythrough-formed annulus 5 and a second housing half shaped as athrough-formed annulus 6, which are interconnected in a liquid-proofmanner along their flanged rims 5a, 6a and 5b, 6c to form together anannular channel 7 in which are enclosed a number of large rolling bodies8, which during operation act as unbalance compensating weights. Theremaining space of the annular channel 7 is at least partly filled witha damping liquid, 7a e.g. oil, which also has an effect during operationof pulling along the rolling bodies 8 until they have settled in theirbalancing positions.

The outer flanged rim 5a of the first housing half 5 and the outerflanged rim 6a of the second housing half 6 in interconnected positionform between them a seat 9 for a separate race track ring 10 having atorus-shaped section forming a groove 11 with a curved concave profilefacing the centre of the ring 10. The groove 11 of the race track ring10 in mounted position is concentric with the axis A of the rotarysystem and in mounted position the race track ring 10 is given radialrigidity and axial alignment by the seat 9 in which the race track ring10 is firmly attached, e.g. by clamping, by press fit, by glueing or thelike. The seat surface in the seat 9 and the torus-shaped groove 11furthermore are also preferably concentric to each other. Thetorus-shaped groove 11 of the race track ring 10 has a hard,substantially smooth surface, and although it is almost to be consideredas a wire ring and in spite of its slender shape, it will provide a welldefined race track for the rolling bodies 10. Therefore the flanged rims5a and 6a are positioned just outside the race track ring, therebyproviding radial rigidity to the ring 10, i.e. in the direction of themain forces from the rolling bodies 8, acting on the race track ring. Inthe embodiment shown, an extended flange 6b of rim 6a at the outer sideof the second housing half 6 and the inner flanged rim 6c of saidhousing half 6 are used for firmly connecting the housing of theautobalancing device to supporting plates 12 or the like, whichcontribute in increasing the rigidity and stability of thelarge-diameter loop formed by the race track wire 10. These supportingplates 12 can be a gable of the washing machine drum 1.

As shown in FIG. 3 the thread-formed race track ring 10 can be formedfrom a straight thin rod or wire, which is bent to an annular shape andhaving its ends fixedly connected, e.g. by a butt welding joint 13. Theends of the bar or wire can also be cut obliquely, thus that the ring 12is not a closed loop but has a oblique slot (not shown).

The housing portions 5, 6 are preferably formed from sheet metalprofiles, which are easily shaped, assembled and fixedly connected to arotary portion of an large size rotary system, such as the washingmachine drum 1. It thus is possible to assemble a entire autobalancingdevice 4 including filling it with damping liquid 7a, at a manufacturingsite and to deliver it from there to manufacturer of the rotary systemfor easy fitting of the autobalancing device in the desired position.

The autobalancing device 4 according to the present invention can ofcourse be directly integrated in the system to which it shall beapplied. For a gable wall of the washing machine drum 1 can be used as ahousing portion thereof, etcetera.

In FIG. 4 finally is shown an autobalancing device 4' according to theinvention, wherein the housing forming the channel 7 for the rollingbodies 8, is formed with a circular cross-section, preferably as athick-walled hose or tube 14, made from a moldable material, preferablya plastic material, and where a race track ring 10, having the sameproperties and shape as those described in connection with the earlierembodiment, preferably is embedded in the tube material.

The previously described groove 11 defining the race track in the racetrack ring 10 shall preferably be of a somewhat bigger radius ofcurvature than the sphere radius of the rolling body 8, and the rollingbody radius shall most preferably be 70-95% of the torus radius of therace track groove. The rolling bodies 8 and the material of the racetrack ring shall preferably have substantially the same hardness and/oryield strength.

The invention is not limited to the embodiments shown in the drawingsand described in connection thereto, and modifications and variationsare possible within the scope of the appended claims. Although theauto-balancing device according to the invention has been shown anddescribed as provided at a large size rotary system, it is in no waylimited thereto, in spite of the fact that it have its most evidentadvantages in connection with such large size rotary systems.

What is claimed is:
 1. A system comprising:a rotary system having anaxis, and an automatic balancing system, the automatic balancing systemincludingan annular housing; an annular outer race track disposed insaid annular housing and being arranged concentric with and attached tosaid rotary system so as to rotate with said rotary system; and a numberof rolling bodies disposed in said annular housing and freely moveablealong said race track for at least one of dynamic contact and staticcontact with said race track during rotation of said rotary system,wherein said outer race track is provided in a separate ring having atorus-shaped groove forming said race track and having a curved concaveprofile facing the centre of the separate ring, said ring being fixedlyinserted in a portion of said housing, formed as a seat for aseat-surface of the ring and which seat is arranged to stiffen theseparate ring for permitting the ring to maintain the circular form ofthe ring in spite of forces acting upon the ring during operation, saidtorus-shaped groove being positioned concentric with the axis of therotary system.
 2. A device as claimed in claim 1, wherein thetorus-shaped groove of the separate ring has a smooth surface.
 3. Adevice as claimed in claim 1, wherein the separate ring includes aslender wire ring.
 4. A device according to claim 1, wherein the rollingbodies are balls having a sphere radius, and the torus-shaped groove ofthe ring has a radius of curvature slightly larger than the sphereradius of the balls.
 5. A device as claimed in claim 4, wherein thesphere radius of the balls is 70-95% of the radius of curvature of thetorus-shaped groove in the separate ring.
 6. A device as claimed inclaim 1, whereinthe separate ring is formed of a wire, bent into a loopand adapted to its circular shape by said seat in the housing.
 7. Adevice as claimed in claim 6, wherein ends of the bent loop of wireforming the separate ring are fixedly interconnected.
 8. A device asclaimed in claim 6, wherein ends of the bent loop of wire forming theseparate ring are configured and arranged to define an oblique slotbetween the ends of the loop of wire.
 9. A device as claimed in claim 1,wherein the annular housing is defined by at least two through-shapedannular discs joined together at a joint to form between them an annularchannel, a region of the joint having flanged rim portions, said flangedrim portions being joined together to define the seat for the separatering.
 10. A device as claimed in claim 9, wherein the flanged rimportions are shaped so as to clamp the separate ring in the seat.
 11. Adevice as claimed in claim 1, wherein the annular housing is a molded,substantially toroidal tube forming a substantially circular channel,said separate ring being embedded in said tube.
 12. A device as claimedin claim 1, wherein at least a part of the annular housing being a partof said rotary system.
 13. A device as claimed in claim 2, wherein theseparate ring is a slender wire ring.
 14. A device as claimed in claim1, wherein said separate ring and said rolling bodies have the samehardness.
 15. A device as claimed in claim 7, wherein the ends of theloop of wire are fixedly interconnected by a welded joint.
 16. A deviceas claimed in claim 12, wherein said part of said rotary system is aportion of a washing machine drum.
 17. An automatic balancing device anda rotary system comprising:an annular housing having an interior; aplurality of roller bodies located in said interior of said annularhousing; and an annular ring separate from said annular housing andlocated in said interior of said annular housing, said annular ringincluding an annular groove concavely curved in a direction toward acenter of said annular ring, said annular groove defining an outer racetrack for said roller bodies; and a rotary system having a rotation axisand a rotatable portion, said annular ring and said race track beinglocated concentric with the rotation axis of said rotary system, saidannular ring being located radially farther away from said rotation axisthan said roller bodies, said annular housing being attached to saidrotatable portion of said rotary system such that said annular housingrotates with said rotatable portion when said rotatable portion rotates.18. The automatic balancing device of claim 17, wherein said annularhousing defines an annular seat that receives said annular ring.
 19. Theautomatic balancing device of claim 18, wherein said housing is definedby two housing portions that have been joined together.
 20. Theautomatic balancing device of claim 17, wherein said annular housingdefines an annular seat that receives said annular ring, annular seatfor preventing said annular ring from moving relative to said annularhousing in a direction away from said rotation axis and in a directionparallel to said rotation axis.
 21. The automatic balancing device ofclaim 17, wherein said annular housing is at least partially defined bya tube.